The first 90-day report after each and every entry must be done in person. Actually on the DTV you'll probably never do a second 90-day report as you must leave before 180 days or get an extension, in which case immigration would automatically update your 90 day report.
Absolutely no appeal mechanism available to you. You're going to have to give us a lot more detailed information on your submission scheme if you want an opinion on how to resubmit.
Typically no. The main DTV Holder will write a sponsorship letter saying that they will be responsible for the financials of the dependent, and resubmit the funding proof. How old are the dependants?
Another thing if you want to buy more time is to request and buy any extension which you won't be eligible for and you will get a 7-Day extension denied stamp giving you 7 days from the date of application to leave the country.
You can only get dependant status from the main holder of the OA Visa. Suggest you join Thai Visa Advice - Q&A and ask your question for expert answers.